Robert S. Mueller III, in 2013, when he was FBI director. (Saul Loeb/Agence France-Presse/Getty Images)

This post has been updated.

Rudolph W. Giuliani is not the most credible messenger. But he seems pretty sure that Robert S. Mueller III has guaranteed that President Trump won’t be indicted. Giuliani says Mueller's team informed Trump's lawyers that such a thing wasn’t even on the table because the special counsel will follow existing Justice Department guidelines that say presidents can’t be indicted.

This has rubbed a lot of people the wrong way. Those anxiously waiting for Mueller to take down Trump cried foul. “My own view is that [the president] can be indicted,” Sen. Richard Blumenthal (D-Conn.) told MSNBC on Thursday. Some see this as a clear abdication of Mueller’s responsibility in holding Trump accountable — or worse, an admission that a president is “above the law.”

Here’s what we can say about this:

It seems eminently plausible — if not likely — that Mueller's team actually provided this assurance.

Mueller may be setting expectations for what will come of all this.

Indicting Trump would be a recipe for huge political unrest.

The timing of the assurance is key here. According to Giuliani, it was provided in a meeting a few weeks ago. This was notably after word leaked that Mueller had told Trump’s lawyers that Trump wasn’t a criminal target of the investigation. Given that, it seems likely Mueller’s team knew this would also leak out.

As I wrote at the time, the previous disclosure was perhaps the first real indication that Mueller didn’t believe he could indict Trump. Some (rather optimistically) hoped Mueller was baiting the president into a false sense of security ahead of Trump testifying, but the most likely explanation was that Trump wasn't a criminal target because Mueller didn’t believe he could be one. Justice Department guidelines that say this were drafted in 1974 and reaffirmed in 2000.

But, Trump opponents may say, guidelines are just that: guidelines. Guidelines aren't even technically rules. That’s true, but they are based upon interpretations of rules, and going outside of them would lead to a legal case. So not only would we have a potential indictment of a president, but we’d have to have a legal case over whether that indictment was lawful in the first place.

Which brings us to the “witch hunt.” Lots and lots of people agree with Trump that the Mueller investigation is indeed a witch hunt. A Quinnipiac University poll last month showed 82 percent of Republicans and 44 percent of all Americans believe that. Imagine that Mueller attempts to indict Trump, despite previous Justice Department guidance that says “the indictment and criminal prosecution of a sitting President ... [would] violate the constitutional separation of powers.” However valid you think the cries of witch hunt are right now, this would certainly throw fuel on the fire and perhaps even lend legitimacy to that claim. Mueller would be doing something that the same Justice Department that appointed him has long said would “violate the constitutional separation of powers.” (Not to mention he would be doing all of this after he said Trump wasn't a criminal target of the investigation.)

This is a practical and political argument rather than a moral one, of course. And people will rightly point out that politics — including the increasingly bare-knuckles politics employed by Trump throughout this process — shouldn’t influence Mueller’s decisions. We should all hope that these decisions are made in something approaching a political vacuum. But when you're stepping outside the normal bounds of Justice Department guidelines, practical considerations must be made.

Anyone in Mueller’s situation has to recognize what’s feasible, and what’s likely to lead to an actually conclusion for the American people. And there are two remedies in place for Congress and the American people to render verdicts: impeachment and the 2020 campaign, respectively. Mueller could even lay out a criminal case while not charging Trump, or name him an unindicted co-conspirator (if the evidence exists, of course).

An indictment of Trump, though, would be inherently and legally controversial, and that's why it makes sense that Mueller both wouldn’t do it and wouldn’t want to do it.